爸爸:father妈妈:mother哥哥:big brother姐姐:big sister妹妹:younger sister 或者 sis弟弟:younger brother
father 爸爸mother妈妈 brother (哥哥)Little brother(弟弟)sister (姐、妹)Little sister(妹妹)
Father, mother, 姐妹都是sister, 哥哥弟弟都是brother
father; mother; elder brother; elder sister; younger sister; younger brother